Calculating Electrostatic Force Between Pennies with Slight Charge Differences

[Emily_20]

Homework Statement

We know that the magnitudes of the negative charge on the electron and the positive charge on the proton are equal. Suppose, however, that these magnitudes differed from each other by as little as 0.0001%. With what force would two copper pennies, placed 1.0 m apart, repel each other? Estimate any quantities you need that you do not know.

Homework Equations

F=kQ1Q2/r^2

The Attempt at a Solution

I do not know from where to start. I drew a picture of the charges. I do not know how to find the charge from 0.0001% condition. Can you help me please?

 

[gneill]

You could start by estimating the numbers of protons and electrons in a penny. You may need to consult the periodic table...